using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

using System.Collections.ObjectModel;

using System.Runtime.Serialization;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/59625363/how-to-set-floatparsehandling-decimal-for-custom-jsonconverter

​

    //https://stackoverflow.com/questions/59625363/how-to-set-floatparsehandling-decimal-for-custom-jsonconverter

​

    [Serializable]

    [JsonConverter(typeof(DecimalDbValueJsonConverter))]

    public struct DecimalDbValue : ISerializable

    {

        private readonly Decimal _decValue;

​

        public DecimalDbValue(

            decimal init)

        {

            _decValue = init;

        }

​

        [JsonConstructor]

        public DecimalDbValue(

            decimal? init)

        {

            if (init.HasValue)

                _decValue = init.Value;

            else

                _decValue = decimal.MinValue;

        }

​

        private DecimalDbValue(

            SerializationInfo objSerializationInfo,

            StreamingContext objStreamingContext)

        {

            _decValue = objSerializationInfo.GetDecimal("value");

        }

​

        public bool IsNotNull

        {

            get

            {

                return !IsNull;

            }

        }

​

        public bool IsNull

        {

            get

            {

                return _decValue.Equals(Decimal.MinValue);

            }

        }

​

        public Decimal Value

        {

            get

            {

                return _decValue;

            }

        }

​

        public void GetObjectData(

            SerializationInfo info,

            StreamingContext context)

        {

            info.AddValue("value", _decValue);

        }

    }

​

    class DecimalDbValueJsonConverter : JsonConverter

    {

        public override bool CanConvert(Type objectType)

        {

            return typeof(DecimalDbValue) == objectType;

        }

​

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

        {

            var value = reader.Value == null ? (decimal?)null : Convert.ToDecimal(reader.Value);

            return new DecimalDbValue(value);

        }

​

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            var dbValue = (DecimalDbValue)value;

            if (dbValue.IsNull)

                writer.WriteNull();

            else

                writer.WriteValue(dbValue.Value);

        }

    }

​

    public class FloatParseHandlingConverter : JsonConverter

    {

        readonly FloatParseHandling floatParseHandling;

​

        public FloatParseHandlingConverter(FloatParseHandling floatParseHandling)

        {

            this.floatParseHandling = floatParseHandling;

        }

​

        public override bool CanConvert(Type objectType)

        {

            throw new NotImplementedException();

        }

​

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

        {

            if (reader.TokenType == JsonToken.Null)

                return null;

            var old = reader.FloatParseHandling;

            try

            {

                reader.FloatParseHandling = floatParseHandling;

                existingValue = existingValue ?? serializer.ContractResolver.ResolveContract(objectType).DefaultCreator();

                serializer.Populate(reader, existingValue);

                return existingValue;

            }

            finally

            {

                reader.FloatParseHandling = old;

            }

        }

​

        public override bool CanWrite { get { return false; } }

​

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            throw new NotImplementedException();

        }

    }

​

    public abstract class RootObject

    {

        public DecimalDbValue Value { get; set; }

    }

​

    [JsonConverter(typeof(FloatParseHandlingConverter), FloatParseHandling.Decimal)]

    public class RootObjectWithConverterApplied : RootObject

    {

    }

​

    public class RootObjectWithoutConverterApplied : RootObject

    {

    }

​

    class TestClass

    {

        public static void Test()

        {

            TestMaxDecimalDbValueWithRootObjectWithConverterApplied();

            TestMaxDecimalDbValueWithRootObjectWithoutConverterApplied();

        }   

        public static void TestMaxDecimalDbValueWithRootObjectWithConverterApplied()

        {

            Console.WriteLine("\nTesting {0}:", nameof(RootObjectWithConverterApplied));

            var root = new RootObjectWithConverterApplied { Value = new DecimalDbValue(decimal.MaxValue) };

            var json = JsonConvert.SerializeObject(root, Formatting.Indented);

            var x = JsonConvert.DeserializeObject<RootObjectWithConverterApplied>(json);

​

            Assert.AreEqual(root.Value.Value, x.Value.Value, string.Format("{0} did not round-trip!", root));

            Console.WriteLine("{0} round-tripped successfully.", root);

        }

        public static void TestMaxDecimalDbValueWithRootObjectWithoutConverterApplied()

        {

            Console.WriteLine("\nTesting {0}:", nameof(RootObjectWithoutConverterApplied));

​

            var root = new RootObjectWithoutConverterApplied { Value = new DecimalDbValue(decimal.MaxValue) };

            var json = JsonConvert.SerializeObject(root, Formatting.Indented);

            var x = JsonConvert.DeserializeObject<RootObjectWithoutConverterApplied>(json);

​

            Assert.AreEqual(root.Value.Value, x.Value.Value, string.Format("{0} did not round-trip!", root));

            Console.WriteLine("{0} round-tripped successfully.", root);

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1})", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , GetNetCoreVersion());

            Console.WriteLine("Json.NET version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.CodeBase.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return null;

        }

    }

#if false

@toebens - if `DecimalDbValue` is the **root object** then `FloatParseHandlingConverter` won't work because it needs to be applied to the container type.  Applying it to `DecimalDbValue` itself won't work because the  decimal value will already have been read in as a `double` by the time `ReadJson()` is called.  In such a situation, you need to set `JsonSerializerSettings.FloatParseHandling` explicitly.  But when not the root object, applying `FloatParseHandlingConverter` to the container will work.  See https://dotnetfiddle.net/BmgKYj.

#endif

​